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#
#
# Nimrod's Runtime Library
# (c) Copyright 2011 Alex Mitchell
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## :Author: Alex Mitchell
##
## This module implements operations for the built-in `seq`:idx: type
## which were inspired by functional programming languages.
##
## **Note**: This interface will change as soon as the compiler supports
## closures and proper coroutines.
proc concat*[T](seqs: openarray[seq[T]]): seq[T] =
## Takes several sequences' items and returns them inside of one sequence.
var L = 0
for seqitm in items(seqs): inc(L, len(seqitm))
newSeq(result, L)
var i = 0
for s in items(seqs):
for itm in items(s):
result[i] = itm
inc(i)
proc distnct*[T](seq1: seq[T]): seq[T] =
## Removes duplicates from a sequence and returns it.
result = @[]
for itm in items(seq1):
if not result.contains(itm): result.add(itm)
proc zip*[S, T](seq1: seq[S], seq2: seq[T]): seq[tuple[a: S, b: T]] =
## Combines two sequences. If one sequence is too short,
## the remaining items in the longer sequence are discarded.
var m = min(seq1.len, seq2.len)
newSeq(result, m)
for i in 0 .. m-1: result[i] = (seq1[i], seq2[i])
iterator filter*[T](seq1: seq[T], pred: proc(item: T): bool): T =
## Iterates through a sequence and yields every item that fulfills the
## predicate.
for i in countup(0, len(seq1) -1):
var item = seq1[i]
if pred(item): yield seq1[i]
proc filter*[T](seq1: seq[T], pred: proc(item: T): bool): seq[T] =
## Returns all items in a sequence that fulfilled the predicate.
accumulateResult(filter(seq1, pred))
template filterIt*(seq1, pred: expr): expr =
## Finds a specific item in a sequence as long as the
## predicate returns true. The predicate needs to be an expression
## containing ``it``: ``filterIt("abcxyz", it == 'x')``.
block:
var result: type(seq1) = @[]
for it in items(seq1):
if pred: result.add(it)
result
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